(57) An improved adaptive pressure control which accounts for nonlinearity in the relationship between fluid pressure and shift time. To account for nonlinearity in the relationship between cumulative shift time error and corrective pressure, the control utilizes an empirically derived table of shift time vs. controlled pressure to develop a raw pressure error in lieu of a shift time error. The adaptive pressure correction, in turn, is developed in relation to the cumulative pressure error. This removes the effect of system nonlinearity from the adaptive control, allowing more accurate adaptive convergence than was heretofore achieved.